Korea Multi-Purpose Satellite-3A (KOMPSAT-3A), the first Korean satellite with optical and infrared sensor, was launched by a Dnepr on 26 March 2015 at Yasny, Russia. Once it was separated from the launch vehicle at 528km mean altitude, autonomous initial operation was activated for solar array deployment, gyro selection, safe-hold mode heater control and thruster-based sun pointing attitude control. Since the first contact by a ground station, the initial activation and checkout was started. For stable early operation using at least one contact per an orbit, several ground stations including KARI station, Sejong station and some abroad stations were utilized. The overall satellite characteristics were demonstrated by first imaging operation results on second day after launch. The initial activation and checkout was performed for 1 week which is relatively short period than that of previous KOMPSAT series. For example, the bus IAC was finished in 3 days which was took 6 days for KOMPSAT-3. Based on successful early operation experience of KOMPSAT-3 and KOMPSAT-5, the IAC procedures could be simplified and absolute timed commands (ATCs) which can be activated during non-contact period by commanding during contact were utilized. The checkout result done by ATC was verified by analyzing playback file. Although the procedures were quickly performed, the satellite was operated safely by prepared contingency operation for every possible unwanted situation. About thirty ready procedures were prepared for various satellite situations which can be occurred during early operation. Eight contingency action sheets were prepared for possible failures during early operation. Furthermore, because the early operation members had been trained by six LEOP rehearsals, any unwanted situation could be controlled immediately. In this paper, the early operation results of KOMPSAT-3A were described. Especially, specific explanation for the bus initial activation and checkout results might give an example of safe and efficient early operation methodology. The described technical details would be reference for the future KOMPSAT mission operation or other similar missions.

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A number of algorithms have been proposed for estimating the magnetometer bias without the spacecraft attitude knowledge . The simplest is the scalar checking which minimizes the differences in the squares of the magnitudes of the measured and modeled magnetic fields. This approach is that the cost function is presented as forth order equation with respect to the magnetometer bias and therefore is required to find global minimum . Magnetometer bias estimation using the genetic algorithm was proposed . New estimation method was the same structure like TWOSTEP. The genetic algorithm provides the initial estimate to find the final solution . The proposed bias estimation using genetic algorithm was compared with other optimization algorithm like the gradient method and TWOSTEP.

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